Peroxisome proliferator activated receptor (PPAR)-α controls the expression of multiple genes involved in lipid metabolism, and activators of PPAR-α, such as fibrates, are commonly used drugs in the treatment of hypertriglyceridemia and other dyslipidemic states. Recent data have also suggested a role for PPAR-α in insulin resistance and glucose homeostasis. In the present study, we have assessed the transcriptional and physiological responses to PPAR-α activation in a diet-induced rat model of insulin resistance. The two PPAR-α activators, fenofibrate and Wy-14643, were dosed at different concentrations in high-fat fed Sprague-Dawley rats, and the transcriptional responses were examined in liver using cDNA microarrays. In these analyses, 98 genes were identified as being regulated by both compounds. From this pool of genes, 27 correlated to the observed effect on plasma insulin, including PPAR-α itself and the leukocyte antigen-related protein tyrosine phosphatase (PTP-LAR). PTP-LAR was downregulated by both compounds, and showed upregulation as a result of the high-fat feeding. This regulation was also observed at the protein level. Furthermore, downregulation of PTP-LAR by fenofibric acid was demonstrated in rat FaO hepatoma cells in vitro, indicating that the observed regulation of PTP-LAR by fenofibrate and Wy-14643 in vivo is mediated as a direct effect of the PPAR agonists on the hepatocytes. PTP-LAR is one of the first genes involved in insulin receptor signaling to be shown to be regulated by PPAR-α agonists. These data suggest that factors apart from skeletal muscle lipid supply may influence PPAR-α-mediated amelioration of insulin resistance.

Background: CD4 T cells help B cells produce antibodies following antigen challenge. This response classically occurs in germinal centers (GC) located in B-cell follicles of secondary lymphoid organs (SLO), a site of immunoglobulin isotype switching and affinity maturation. GC formation requires specialized CD4 T cells, T-follicular helper (Tfh) cells, which localize to follicles and provide B cells with survival and differentiation signals that are essential for B-cell maturation into memory and long-lived plasma cells. Pathogenic autoantibodies in human and murine lupus arise in a like manner. Although Tfh cells are critical for GC development, their genesis in humans, role in promotion of autoimmunity, and potential as therapeutic targets in SLE are incompletely understood. To address these issues, we dissected Tfh cell development and function, defining their transcriptional regulation, migration, and function in vivo in normal and lupus-prone mice and ex vivo in normal humans and patients with SLE. Methods: We used a combination of approaches-flow cytometry, confocal microscopy, microarrays, quantitative chromatin immunoprecipitation and DNA sequencing (ChIP-seq), retroviral overexpression, and T-cell-B-cell helper assays-to characterize Tfh cells in normal mice and in lupus-prone strains, and from the tonsils of normal humans and the blood of patients with SLE. Results: We found that the transcription factor Bcl6 (B-cell CLL/lymphoma 6) is necessary and sufficient for Tfh development and function, via genetic control of Tfh proteins that are essential for their migration to B-cell follicles and GC and subsequent B-cell maturation. We dissected steps in Tfh development within SLO, beginning with their genesis in the T-cell zone followed by emigration to sites of B-cell interaction outside the B-cell follicle, where we have shown that B cells serve to provide signals for continued Tfh expansion and follicular migration. We have now begun to tease apart the factors that mediate T-cell-B-cell collaboration in the follicle; these represent therapeutic targets in SLE. Finally, we have shown that patients with SLE have expansion of Tfh cells in the blood, a finding that highlights their potential role in the pathogenesis of SLE and as likely therapeutic targets. Conclusion: These studies help define the developmental pathways for Tfh cells, and the steps that enable these cells to function in the B-cell follicle to promote immunoglobulin and autoantibody production. They have also helped define markers of Tfh cells in normals and autoimmune individuals, and suggest that they are a promising therapeutic target in patients.

Background Upregulation of mRNA IFN-alpha activity (IFN signature) has been demonstrated in some patients with systemic lupus erythematosus (SLE). Based on this observation anti-IFN-alpha mAbs are currently being developed for the treatment of SLE. Interestingly naturally occurring antibodies towards IFN-alpha have previously been demonstrated in a small fraction of healthy individuals, in therapeutic IgG preparations and in patients with inflammatory disorders. Objectives Recently naturally occurring antibodies against a single IFN alpha subtype were observed in SLE patients. A high level of such anti-IFN antibodies could theoretically affect the IFN gene signature and clinical disease activity. Therefore we carried out a longitudinal study of IFN activity, anti-IFN antibodies (frequency, titre, neutralizing capacity, specificity) and disease activity in a cohort of SLE patients. Methods Peripheral blood mononuclear cells (PBMC) and plasma samples were collected over an average of 6 visits (range 2-12) from 23 SLE patients (median SLEDAI score at initiation 6 (range 0-35) and 5 healthy donors. Patients were followed from 197 to 812 days. Plasma levels of autoantibodies towards a mixture of IFN-alpha 1, 2- and 8 or the individual subtypes were measured by radioimmunoassay, and 44 other autoantibodies were evaluated in a multiplex luminex system by Rules-Based-Medicine. The mRNA IFN signature was deduced from full transciptome analyses in PBMCs using Human Genome U133 Plus 2.0 arrays and RT-PCR. Results In healthy donors no autoantibodies towards IFN-alpha were detected; in alignment with historic data where the frequency is 3-5/1.000 individuals. In contrast, we detected specific anti-IFN-alpha antibodies in 4/23 (17%) of the patients. In three of these, the autoantibodies were present throughout the study while the last patient developed autoantibodies between visits 5 and 6. In one of the patients very high titres of antibodies to the IFN mixture and against the individual IFN subtypes were demonstrated while the other patients had lower titres. The antibodies in the highly positive patient demonstrated increasing neutralizing capacity throughout the study. The four anti-IFN-alpha-positive patients did not demonstrate an increased level of other autoantibodies when compared to anti-IFN antibody negative patients. A composite score of 12 well characterized IFN-alpha inducible genes (IFN signature) was defined. A 1.2 to 4-fold fluctuation in the IFN-score was observed over time in the individual patients. The patient with high levels of neutralizing anti-IFN antibodies showed significantly reduced IFN signature activity during the study. Conclusions Anti-IFN autoantibodies are present in a subset of SLE patients. An association of anti-IFN alpha 4 antibodies and disease activity has previously been reported, and our study confirms this for additional IFN-alpha subtypes. Naturally occurring autoantibodies against IFN-alpha could affect treatment outcome following anti-IFN mAb therapy. Disclosure of Interest C...